Cell Membrane & Passive Transport: EQ: Can I diagram diffusion of oxygen, facilitated diffusion of glucose, and osmosis across a cell membrane?

BOUNDARY OF THE CELL Cell: smallest unit that can carry out all the activities for life. (the “atom” of biology)

Cell Membrane Outside of cell Inside of cell (cytoplasm) Carbohydrate Proteins Protein channel Lipid bilayer Carbohydrate chains

Membrane structure Fluid Mosaic Model—Proteins “float” in a fluid or moveable layer of phospholipids Semi-Permeable—certain molecules can pass through the membrane, but not all molecules can

The Structure of the Cell Membrane Outside of cell Inside (cytoplasm) Cell membrane Proteins Protein channel Lipid bilayer Carbohydrate chains Proteins—act as channels or pumps to help molecules pass through the membrane Carbohydrate chains—help cells recognize and communicate with each other Phospholipid bilayer— phospholipids have a phosphate head (yellow circle) lipid tails (the brown tails). The phosphates line up on the outside because they are hydrophilic (water-loving). The lipid tails line up on the inside because they are hydrophobic (water-hating).

Review of solution terms: Solution – mixture of solute and solvent Solute – substance being dissolved Solvent – substance dissolving solute (Universal Solvent)-Water

Membrane traffic Passive transport~ diffusion of a substance across a biological membrane (NO ENERGY) [] = concentration Diffusion~ the overall movement of particles from a region of high [] to an area of low [] Osmosis~ the diffusion of water across a selectively permeable membrane

Results of Diffusion Dynamic equilibrium Homeostasis Once diffusion has evenly distributed the solute throughout the solvent; movement of particles continues with no change in [] Homeostasis Preservation of equilibrium

Diffusion depends on [] gradient [] gradient: the difference in [] of a substance across space Diffusion is said to move down a [] gradient Diffusion continues until there is NO [] gradient Ex: O2 diffuses into oxygen depleted blood

Diffusion Small molecules like WATER, OXYGEN, AND CARBON DIOXIDE can move in and out freely. Large molecules like PROTEINS AND CARBOHYDRATES CANNOT Charged IONS CANNOT

Osmosis~ the diffusion of water across a selectively permeable membrane

Osmosis in the Real World Bryophytes, or mosses, are plants that depend on osmosis transfer water from the environment into the plant. Bryophytes can never grow tall, because they cannot pull the water against gravity just using the concentration gradient. Bryophytes must also live in wet environments

Questions Osmosis is the diffusion of _______ across a cell membrane. Osmosis and Diffusion are both types of __________ transport. Passive transport does or does not require energy? Small molecules can not move across freely. T or F Large molecules can move freely. T or F

Three Different Types of Solutions Isotonic Solution Hypotonic Solution Hypertonic Solution

Isotonic Solution The solute outside the cell is equal in concentration to the solute in the cell. The cell retains its shape. water moves equally in both directions

Hypotonic Solutions Solution outside the blood cell contains a lower [] of solute than inside of the cell. Water will diffuse in. cell will lyse (burst). Animal cells - cytolysis. Plant cells do not burst- turgur pressure— grocers use this idea

Cells in a Hypotonic Solution

Hypertonic Solutions The solution outside the cell has a higher [] of solute than inside of the cell. Water will diffuse out of the cell, causing the cell to shrink or crenate Why should you not salt meat before cooking? CRENATION PLASMOLYSIS

Cells in a Hypertonic Solution

In what type of solution would these cells be found?

Water Balance Summary Osmoregulation~ control of water balance Hypertonic~ higher concentration of solutes Hypotonic~ lower concentration of solutes Isotonic~ equal concentrations of solutes

Plasmolysis Turgidity in plant cells.

What type of solution is this? Hypertonic What will happen to the cell? It will shrink.